Electronic throttle controls or “ETCs” are well known for controlling the movement of a throttle plate within a throttle body that operates to control the amount of air delivered to an internal combustion engine. The ETC receives signals from the engine and/or the electronic control unit (ECU) of the vehicle directing the ETC to move the throttle plate to a degree dictated by the air requirements of the engine condition. It is also known that the throttle plate may sometimes become stuck due to icing or coke formation, for example. When this occurs, the ETC sets throttle actuation faults directing the throttle blade to move to a slightly open position which allows only enough air to reach the engine for a “limp home” condition. If the throttle is stuck in a near or fully open position, the ETC system detects this and reduces the available power to idle only or may completely disable the engine in some cases.
ETC systems have been developed in the past directed toward removing the obstruction from the throttle plate such as seen in commonly owned, co-pending U.S. patent application Ser. No. 11/262,022, the disclosure of which is incorporated herein by reference. In the '022 application, a piezo electronic actuator is disclosed which is operable to apply a high force to the throttle plate gear to free the plate from the stuck position. While the system of the '022 application provides an effective means for freeing a stuck throttle blade, it works from the standpoint that an obstruction has already formed which is preventing the throttle plate from moving correctly. Furthermore, should the obstruction become very large, the force required to free the stuck throttle plate may exceed the maximum force of the piezo actuator.
When an engine is running, the temperature of the engine and surrounding components can be very hot. Once the engine is shut off, the engine begins to cool until it is in equilibrium with the ambient temperature. The period of time from engine shut off to engine temperature equilibrium with the ambient is termed “engine soak” to the those skilled in the art. In cold climates, the engine temperature can thus dip below freezing temperatures as it goes through engine soak. In this situation, any moisture around the throttle plate will freeze and present a potential block to proper throttle movement once the engine is started again. Other matter such as coke can also form around a throttle plate.
There therefore exists a need for an ETC system and method directed at clearing potential or partly formed obstructions near the throttle plate during engine soak.